Polyurethane urea polishing pad

ABSTRACT

The present invention relates to an article for altering a surface of a workpiece, or a polishing pad having a window. In particular, the polishing pad includes a polyurethane urea material wherein the polyurethane urea material contains cells which are at least partially filled with gas. The polyurethane urea material can be prepared by combining polyisocyanate and/or polyurethane prepolymer, hydroxyl-containing material, amine-containing material and blowing agent. The polishing pad according to the present invention is useful for polishing articles, and is especially useful for chemical mechanical polishing or planarization of microelectronic and optical electronic devices such as but not limited to semiconductor wafers. The window of the polishing pad is at least partially transparent and thus, can be particularly useful with polishing or planarizing tools that are equipped with through-the-platen wafer metrology.

The present invention relates to an article for altering a surface of aworkpiece. In particular, the present invention is directed to apolishing pad having a window. More particularly, the polishing layer ofthe pad can include a polyurethane urea material wherein cells at leastpartially filled with gas are substantially uniformly distributedthroughout at least a portion of the material and/or pad. Thepolyurethane urea material can be prepared by combining polyisocyanateand/or polyurethane prepolymer, hydroxyl-containing material,amine-containing material and blowing agent. The polishing pad accordingto the present invention is useful for polishing articles, and isespecially useful for chemical mechanical polishing or planarization ofmicroelectronic and optical electronic devices such as but not limitedto semiconductor wafers. The window of the polishing pad is at leastpartially transparent and thus, can be particularly useful withpolishing or planarizing tools that are equipped with through-the-platenwafer metrology.

The polishing or planarization of a rough surface of an article such asa microelectronic device, to a substantially smooth surface generallyinvolves rubbing the rough surface with the work surface of a polishingpad using a controlled and repetitive motion. A polishing fluid can beinterposed between the rough surface of the article that is to bepolished and the work surface of the polishing pad.

The fabrication of a microelectronic device can comprise the formationof a plurality of integrated circuits on a semiconductor substrate. Thecomposition of the substrate can include silicon or gallium arsenide.The integrated circuits generally can be formed by a series of processsteps in which patterned layers of materials, such as conductive,insulating and semi-conducting materials, are formed on the substrate.In order to maximize the density of integrated circuits per wafer, it isdesirable to have a planar polished substrate at various stagesthroughout the production process. As such, production of amicroelectronic device typically involves at least one polishing stepand can often involve a plurality of polishing steps, which can resultin the use of more than one polishing pad.

The polishing step can include rotating the polishing pad and thesemiconductor substrate against each other in the presence of apolishing fluid. The polishing fluid can be mildly alkaline and canoptionally contain an abrasive particulate material such as but notlimited to particulate cerium oxide, particulate alumina, or particulatesilica. The polishing fluid can facilitate the removal and transport ofabraded material off and away from the rough surface of the article.

Polishing pad characteristics such as pore volume and pore size can varyfrom pad-to-pad and throughout the operating lifetime of a particularpad. Variations in the polishing characteristics of the pads can resultin inadequately polished and planarized substrates which can beunsuitable for fabricating semiconductor wafers. Thus, it is desirableto develop a polishing pad that exhibits reduced pad-to-pad variation inpolishing and planarization characteristics. It is further desirable todevelop a polishing pad that exhibits reduced variations in polishingand planarization characteristics throughout the operating lifetime ofthe pad.

Planarizing tools having the ability to measure the progress of theplanarization process while the wafer is held in the tool and in contactwith the pad are known in the art. Measuring the progress of planarizinga microelectronic device during the planarizing process can be referredto in the art as “in-situ metrology”. U.S. Pat. Nos. 5,964,643 and6,159,073, and European Patent 1,108,501 describe polishing orplanarizing tools and in-situ metrology systems. In general, in-situmetrology can include directing a beam of light through an at leastpartially transparent window located in the platen of the tool; the beamof light can be reflected off the surface of the wafer, back through theplaten window, and into a detector. The polishing pad can include awindow that is at least partially transparent to the wavelengths used inthe metrology system, and essentially aligned with the planten window.

Thus, it is desirable to develop a polishing pad that comprises a windowarea useful for in-situ metrology. It is further desirable that thewindow provides suitable transparency throughout the operating life ofthe pad.

One disadvantage with known pads having windows which are coplanar withthe polishing surface, can include wearing of the window portion at aslower rate than the pad surface. A further disadvantage with known padshaving a coplanar window can include scratching of the window as aresult of its contact with abrasive particles in the slurry during thepolishing or planarization process. A scratched window can generallyreduce the transparency of the window and can cause an attenuation ofthe metrology signal.

For the purposes of this specification, unless otherwise indicated, allnumbers expressing quantities of ingredients, reaction conditions, andso forth used in the specification and claims are to be understood asbeing modified in all instances by the term “about.” Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties sought to be obtained by thepresent invention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

The present invention includes a pad adapted to polish a microelectronicsubstrate. The pad includes a polyurethane urea-containing polishinglayer. The polishing layer can include at least partially gas-filledcells, at least a portion of the at least partially gas-filled cells canbe formed by an in-situ reaction. The polishing layer has an openingformed therein. The pad of the present invention includes a second layerwherein at least a portion of the second layer can include an at leastpartially transparent window. The polishing layer is at least partiallyconnected to the second layer, and the opening in the polishing layer isat least partially aligned with the window of the second layer.

The present invention includes a polishing pad having a window. Thepolishing pad can include a first layer and a second layer. The secondlayer can be at least partially connected to the first layer. The term“connected to” means to link together or place in relationship eitherdirectly, or indirectly by one or more intervening materials. The firstlayer can function as the work surface or the polishing layer of thepad. The polishing layer can at least partially interact with thesubstrate to be polished and the polishing slurry. In a non-limitingembodiment, at least a portion of the second layer of the pad cancomprise a window which is at least partially transparent to wavelengthsused by the metrology instrumentation of polishing tools. In anon-limiting embodiment, the polishing pad of the present invention caninclude a sub-pad layer at least partially connected to the secondlayer. In a non-limiting embodiment, the cells can be substantiallyuniformly distributed throughout the material and/or polishing layer.

In alternate non-limiting embodiments, the polyurethane urea of thepresent invention can be prepared by combining a polyisocyanate withhydroxyl-containing material, amine-containing material and blowingagent; or by reacting a two-component composition comprising combiningpolyisocyanate and hydroxyl-containing material to form a polyurethaneprepolymer, and then reacting the prepolymer with amine-containingmaterial and blowing agent; or by combining polyisocyanate and/orpolyurethane prepolymer, optional hydroxyl-containing material,amine-containing material and blowing agent.

In alternate non-limiting embodiments, the amount of polyisocyanate,hydroxyl-containing material and amine-containing material can beselected such that the equivalent ratio of (NCO+NCS):(NH+OH) can begreater than 0.95, or at least 1.0, or at least 1.05, or less than 1.3,or less than 1.2, or less than 1.1.

Polyisocyanates useful in the preparation of the polyurethane urea ofthe present invention are numerous and widely varied. Suitablepolyisocyanates can include but are not limited to polymeric and C₂-C₂₀linear, branched, cyclic and aromatic polyisocyanates. Non-limitingexamples can include polyisocyanates having backbone linkages chosenfrom urethane linkages (—NH—C(O)—O—).

The molecular weight of the polyisocyanate can vary widely. In alternatenon-limiting embodiments, the number average molecular weight (Mn) canbe at least 100 grams/mole, or at least 150 grams/mole, or less than15,000 grams/mole, or less than 5000 grams/mole. The number averagemolecular weight can be determined using known methods. The numberaverage molecular weight values recited herein and the claims weredetermined by gel permeation chromatography (GPC) using polystyrenestandards.

Non-limiting examples of suitable polyisocyanates can include but arenot limited to polyisocyanates having at least two isocyanate groups.

Non-limiting examples of polyisocyanates can include but are not limitedto aliphatic polyisocyanates, cycloaliphatic polyisocyanates wherein oneor more of the isocyanato groups are attached directly to thecycloaliphatic ring, cycloaliphatic polyisocyanates wherein one or moreof the isocyanato groups are not attached directly to the cycloaliphaticring, aromatic polyisocyanates wherein one or more of the isocyanatogroups are attached directly to the aromatic ring, and aromaticpolyisocyanates wherein one or more of the isocyanato groups are notattached directly to the aromatic ring.

In a non-limiting embodiment of the present invention, thepolyisocyanate can include but is not limited to aliphatic orcycloaliphatic diisocyanates, aromatic diisocyanates, cyclic dimers andcyclic trimers thereof, and mixtures thereof. Non-limiting examples ofsuitable polyisocyanates can include but are not limited to Desmodur N3300A (hexamethylene diisocyanate trimer) which is commerciallyavailable from Bayer; Desmodur N 3400 (60% hexamethylene diisocyanatedimer and 40% hexamethylene diisocyanate trimer).

In a non-limiting embodiment, the polyisocyanate can includedicyclohexylmethane diisocyanate and isomeric mixtures thereof. As usedherein and the claims, the term “isomeric mixtures” refers to a mixtureof the cis-cis, trans-trans, and cis-trans isomers of thepolyisocyanate. Non-limiting examples of isomeric mixtures for use inthe present invention can include the trans-trans isomer of4,4′-methylenebis(cyclohexyl isocyanate), hereinafter referred to as“PICM” (paraisocyanato cyclohexylmethane), the cis-trans isomer of PICM,the cis-cis isomer of PICM, and mixtures thereof.

In one non-limiting embodiment, the PICM used in this invention can beprepared by phosgenating the 4,4′-methylenebis(cyclohexyl amine) (PACM)by procedures well known in the art such as the procedures disclosed inU.S. Pat. Nos. 2,644,007 and 2,680,127 which are incorporated herein byreference. The PACM isomer mixtures, upon phosgenation, can produce PICMin a liquid phase, a partially liquid phase, or a solid phase at roomtemperature. The PACM isomer mixtures can be obtained by thehydrogenation of methylenedianiline and/or by fractional crystallizationof PACM isomer mixtures in the presence of water and alcohols such asmethanol and ethanol.

In a non-limiting embodiment, the isomeric mixture can contain from10-100 percent of the trans,trans isomer of 4,4′-methylenebis(cyclohexylisocyanate)(PICM).

In a non-limiting embodiment, the polyisocyanate can include2,4-tolylene diisocyanate; 2,6-tolylene diisocyanate and mixtures ofthese isomers (“TDI”).

Additional aliphatic and cycloaliphatic diisocyanates that can be usedin alternate non-limiting embodiments of the present invention include3-isocyanato-methyl-3,5,5-trimethyl cyclohexyl-isocyanate (“IPDI”) whichis commercially available from Arco Chemical, and meta-tetramethylxylenediisocyanate (1,3-bis(1-isocyanato-1-methylethyl)-benzene) which iscommercially available from Cytec Industries Inc. under the tradenameTMXDI.RTM. (Meta) Aliphatic Isocyanate.

As used herein and the claims, the terms aliphatic and cycloaliphaticdiisocyanates refer to 6 to 100 carbon atoms linked in a straight chainor cyclized having two diisocyanate reactive end groups. In anon-limiting embodiment of the present invention, the aliphatic andcycloaliphatic diisocyanates for use in the present invention caninclude TMXDI and compounds of the formula R—(NCO)₂ wherein R representsan aliphatic group or a cycloaliphatic group.

Further non-limiting examples of suitable polyisocyanates can includebut are not limited to aliphatic polyisocyanates; ethylenicallyunsaturated polyisocyanates; alicyclic polyisocyanates; aromaticpolyisocyanates wherein the isocyanate groups are not bonded directly tothe aromatic ring, e.g., α,α′-xylene diisocyanate; aromaticpolyisocyanates wherein the isocyanate groups are bonded directly to thearomatic ring, e.g., benzene diisocyanate; halogenated, alkylated,alkoxylated, nitrated, carbodiimide-modified, urea-modified andbiuret-modified derivatives of polyisocyanates thereof; and dimerizedand trimerized products of polyisocyanates thereof.

Further non-limiting examples of aliphatic polyisocyanates can includeethylene diisocyanate, trimethylene diisocyanate, tetramethylenediisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate,nonamethylene diisocyanate, 2,2′-dimethylpentane diisocyanate,2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate,2,4,4,-trimethylhexamethylene diisocyanate,1,6,11-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate,1,8-diisocyanato-4-(isocyanatomethyl)octane,2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane,bis(isocyanatoethyl)-carbonate, bis(isocyanatoethyl)ether,2-isocyanatopropyl-2,6-diisocyanatohexanoate, lysinediisocyanate methylester and lysinetriisocyanate methyl ester.

Examples of ethylenically unsaturated polyisocyanates can include butare not limited to butene diisocyanate and1,3-butadiene-1,4-diisocyanate. Alicyclic polyisocyanates can includebut are not limited to isophorone diisocyanate, cyclohexanediisocyanate, methylcyclohexane diisocyanate, bis(isocyanatomethyl)cyclohexane, bis(isocyanatocyclohexyl)methane,bis(isocyanatocyclohexyl)-2,2-propane,bis(isocyanatocyclohexyl)-1,2-ethane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptaneand2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane.

Examples of aromatic polyisocyanates wherein the isocyanate groups arenot bonded directly to the aromatic ring can include but are not limitedto bis(isocyanatoethyl)benzene, α,α,α′,α′-tetramethylxylenediisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene,bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene,bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl) phthalate,mesitylene triisocyanate and 2,5-di(isocyanatomethyl)furan. Aromaticpolyisocyanates having isocyanate groups bonded directly to the aromaticring can include but are not limited to phenylene diisocyanate,ethylphenylene diisocyanate, isopropylphenylene diisocyanate,dimethylphenylene diisocyanate, diethylphenylene diisocyanate,diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate,benzene triisocyanate, naphthalene diisocyanate, methylnaphthalenediisocyanate, biphenyl diisocyanate, ortho-toluidine diisocyanate,ortho-tolylidine diisocyanate, ortho-tolylene diisocyanate,4,4′-diphenylmethane diisocyanate,bis(3-methyl-4-isocyanatophenyl)methane, bis(isocyanatophenyl)ethylene,3,3′-dimethoxy-biphenyl-4,4′-diisocyanate, triphenylmethanetriisocyanate, polymeric 4,4′-diphenylmethane diisocyanate, naphthalenetriisocyanate, diphenylmethane-2,4,4′-triisocyanate,4-methyldiphenylmethane-3,5,2′,4′,6′-pentaisocyanate, diphenyletherdiisocyanate, bis(isocyanatophenylether)ethyleneglycol,bis(isocyanatophenylether)-1,3-propyleneglycol, benzophenonediisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate anddichlorocarbazole diisocyanate.

In alternate non-limiting embodiments of the present invention,polyisothiocyanate or a combination of polyisocyanate andpolyisothiocyanate can be used in place of polyisocyanate. In thesealternate non-limiting embodiments, isothiocyanate can have at least twoisothiocyanate groups.

In a non-limiting embodiment of the present invention, thepolyisocyanate for use in the present invention can include polyurethaneprepolymer.

In a non-limiting embodiment, polyisocyanate can be reacted withhydroxyl-containing material to form polyurethane prepolymer, and saidprepolymer can be reacted with amine-containing material and blowingagent to produce the polyurethane urea of the present invention. Inanother non-limiting embodiment, polyisocyanate and polyurethaneprepolymer can be reacted with hydroxyl-containing material,amine-containing material and blowing agent. In a further non-limitingembodiment, polyisocyanate and polyurethane prepolymer can be reactedwith amine-containing material and blowing agent.

Hydroxyl-containing materials are varied and known in the art.Non-limiting examples can include but are not limited to polyols;sulfur-containing materials such as but not limited to hydroxylfunctional polysulfides, and SH-containing materials such as but notlimited to polythiols; and materials having both hydroxyl and thiolfunctional groups.

Suitable hydroxyl-containing materials for use in the present inventioncan include a wide variety of materials known in the art. Non-limitingexamples can include but are not limited to polyether polyols, polyesterpolyols, polycaprolactone polyols, polycarbonate polyols, and mixturesthereof.

Polyether polyols and methods for their preparation are known to oneskilled in the art. Many polyether polyols of various types andmolecular weight are commercially available from various manufacturers.Non-limiting examples of polyether polyols can include but are notlimited to polyoxyalkylene polyols, and polyalkoxylated polyols.Polyoxyalkylene polyols can be prepared in accordance with knownmethods. In a non-limiting embodiment, a polyoxyalkylene polyol can beprepared by condensing an alkylene oxide, or a mixture of alkyleneoxides, using acid- or base-catalyzed addition with a polyhydricinitiator or a mixture of polyhydric initiators, such as but not limitedto ethylene glycol, propylene glycol, glycerol, and sorbitol.Non-limiting examples of alkylene oxides can include ethylene oxide,propylene oxide, butylene oxide, amylene oxide, aralkylene oxides, suchas but not limited to styrene oxide, mixtures of ethylene oxide andpropylene oxide. In a further non-limiting embodiment, polyoxyalkylenepolyols can be prepared with mixtures of alkylene oxide using random orstep-wise oxyalkylation. Non-limiting examples of such polyoxyalkylenepolyols include polyoxyethylene, such as but not limited to polyethyleneglycol, polyoxypropylene, such as but not limited to polypropyleneglycol.

In a non-limiting embodiment, polyalkoxylated polyols can be representby the following general formula:

wherein m and n can each be a positive integer, the sum of m and n beingfrom 5 to 70; R₁ and R₂ are each hydrogen, methyl or ethyl; and A is adivalent linking group such as a straight or branched chain alkylenewhich can contain from 1 to 8 carbon atoms, phenylene, and C₁ to C₉alkyl-substituted phenylene. The chosen values of m and n can, incombination with the chosen divalent linking group, determine themolecular weight of the polyol.

Polyalkoxylated polyols can be prepared by methods that are known in theart. In a non-limiting embodiment, a polyol such as4,4′-isopropylidenediphenol can be reacted with an oxirane-containingmaterial such as but not limited to ethylene oxide, propylene oxide andbutylene oxide, to form what is commonly referred to as an ethoxylated,propoxylated or butoxylated polyol having hydroxy functionality.Non-limiting examples of polyols suitable for use in preparingpolyalkoxylate polyols can include those polyols described in U.S. Pat.No. 6,187,444 B1 at column 10, lines 1-20, which disclosure isincorporated herein by reference.

As used herein and the claims, the term “polyether polyols” can includethe generally known poly(oxytetramethylene) diols prepared by thepolymerization of tetrahydrofuran in the presence of Lewis acidcatalysts such as but not limited to boron trifluoride, tin (IV)chloride and sulfonyl chloride. In a non-limiting embodiment, thepolyether polyol can include Terathane™ polyether glycol which iscommercially available from DuPont. Also included are the polyethersprepared by the copolymerization of cyclic ethers such as but notlimited to ethylene oxide, propylene oxide, trimethylene oxide, andtetrahydrofuran with aliphatic diols such as but not limited to ethyleneglycol, 1,3-butanediol, 1,4-butanediol, diethylene glycol, dipropyleneglycol, 1,2-propylene glycol and 1,3-propylene glycol. Compatiblemixtures of polyether polyols can also be used. As used herein,“compatible” means that the polyols are mutually soluble in each otherso as to form a single phase.

A variety of polyester polyols known in the art can be used in thepresent invention. Suitable polyester polyols can include but are notlimited to polyester glycols. Polyester glycols for use in the presentinvention can include the esterification products of one or moredicarboxylic acids having from four to ten carbon atoms, such as but notlimited to adipic, succinic or sebacic acids, with one or more lowmolecular weight glycols having from two to ten carbon atoms, such asbut not limited to ethylene glycol, propylene glycol, diethylene glycol,1,4-butanediol, neopentyl glycol, 1,6-hexanediol and 1,10-decanediol.Esterification procedures for producing polyester polyols is described,for example, in the article D. M. Young, F. Hostettler et al.,“Polyesters from Lactone,” Union Carbide F-40, p. 147.

In a non-limiting embodiment, the polyol for use in the presentinvention can include polycaprolactone polyols. Suitablepolycaprolactone polyols are varied and known in the art. In anon-limiting embodiment, polycaprolactone polyols can be prepared bycondensing caprolactone in the presence of difunctional active hydrogencompounds such as but not limited to water or low molecular weightglycols as recited herein. Non-limiting examples of suitablepolycaprolactone polyols can include commercially available materialsdesignated as the CAPA series from Solvay Chemical which includes but isnot limited to CAPA 2047A, and the TONE™ series from Dow Chemical suchas but not limited to TONE 0201.

Polycarbonate polyols for use in the presen invention are varied andknown to one skilled in the art. Suitable polycarbonate polyols caninclude those commercially available (such as but not limited toRavecarb™ 107 from Enichem S.p.A.). In a non-limiting embodiment, thepolycarbonate polyol can be produced by reacting an organic glycol suchas a diol, described hereinafter and in connection with the glycolcomponent of the polyurethane or polyurethane urea, and a dialkylcarbonate, such as described in U.S. Pat. No. 4,160,853. In anon-limiting embodiment, the polyol can include polyhexamethyl carbonatesuch as HO—(CH₂)₆—[O—C(O)—O—(CH₂)₆]_(n)—OH, wherein n is an integer from4 to 24, or from 4 to 10, or from 5 to 7.

In a non-limiting embodiment, the glycol material can comprise lowmolecular weight polyols such as polyols having a number averagemolecular weight of less than 500 grams/mole, and compatible mixturesthereof. As used herein, the term “compatible” means that the glycolsare mutually soluble in each other so as to form a single phase.Non-limiting examples of these polyols can include but are not limitedto low molecular weight diols and triols. In a further non-limitingembodiment, the amount of triol chosen can be such to avoid a highdegree of cross-linking in the polyurethane or polyurethane urea. Inalternate non-limiting embodiments, the organic glycol can contain from2 to 16, or from 2 to 6, or from 2 to 10, carbon atoms. Non-limitingexamples of such glycols can include but are not limited to ethyleneglycol, propylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, tripropylene glycol, 1,2-,1,3- and 1,4-butanediol, 2,2,4-trimethyl-1,3-pentanediol,2-methyl-1,3-pentanediol, 1,3- 2,4- and 1,5-pentanediol, 2,5- and1,6-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol,2,2-dimethyl-1,3-propanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol,1,2-bis(hydroxyethyl)-cyclohexane, glycerin, tetramethylolmethane,pentaerythritol, trimethylolethane and trimethylolpropane; and isomersthereof.

In alternate non-limiting embodiments, the hydroxyl-containing materialcan have a molecular weight of at least 200 grams/mole, or at least 1000grams/mole, or at least 2000 grams/mole. In alternate non-limitingembodiments, the hydroxyl-containing material can have a number averagemolecular weight of less than 10,000 grams/mole, or less than 15,000grams/mole, or less than 20,000 grams/mole, or less than 32,000grams/mole.

In a non-limiting embodiment, the hydroxyl-containing material for usein the present invention can include teresters produced from at leastone low molecular weight dicarboxylic acid, such as adipic acid.

In a non-limiting embodiment, the hydroxyl-containing material cancomprise block polymers including blocks of ethylene oxide-propyleneoxide and/or ethylene oxide-butylene oxide. In a non-limitingembodiment, the hydroxyl-containing material can comprise a blockpolymer of the following chemical formula:HO—(O—CRRCRR—Y_(n))_(a)—(CRRCRR—Y_(n)—O)_(b)—(CRRCRR—Y_(n)—O)_(c)—H

wherein R can represent hydrogen or C₁-C₆ alkyl; Y_(n) can representC₀-C₆ hydrocarbon; n can be an integer from 0 to 6; a, b, and c can eachbe an integer from 0 to 300, wherein a, b and c are chosen such that thenumber average molecular weight of the material does not exceed 32,000grams/mole.

In further alternate non-limiting embodiments, hydroxyl-containingmaterials such as but not limited to Pluronic.RTM R, Pluronic.RTM,Tetronic.RTM R and Tetronic.RTM Block Copolymer Surfactants, which arecommercially available from BASF, can be used as the hydroxyl-containingmaterial in the present invention.

Further, non-limiting examples of suitable polyols for use in thepresent invention can include straight or branched chain alkane polyols,such as but not limited to 1,2-ethanediol, 1,3-propanediol,1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, neopentylglycol, trimethylolethane, trimethylolpropane, di-trimethylolpropane,erythritol, pentaerythritol and di-pentaerythritol; polyalkyleneglycols, such as but not limited to diethylene glycol, dipropyleneglycol and higher polyalkylene glycols such as but not limited topolyethylene glycols which can have number average molecular weights offrom 200 grams/mole to 2,000 grams/mole; cyclic alkane polyols, such asbut not limited to cyclopentanediol, cyclohexanediol, cyclohexanetriol,cyclohexanedimethanol, hydroxypropylcyclohexanol andcyclohexanediethanol; aromatic polyols, such as but not limited todihydroxybenzene, benzenetriol, hydroxybenzyl alcohol anddihydroxytoluene; bisphenols, such as, 4,4,-isopropylidenediphenol;4,4′-oxybisphenol, 4,4′-dihydroxybenzophenone, 4,4′-thiobisphenol,phenolphthlalein, bis(4-hydroxyphenyl)methane,4,4′-(1,2-ethenediyl)bisphenol and 4,4′-sulfonylbisphenol; halogenatedbisphenols, such as but not limited to4,4′-isopropylidenebis(2,6-dibromophenol),4,4′-isopropylidenebis(2,6-dichlorophenol) and4,4′-isopropylidenebis(2,3,5,6-tetrachlorophenol); alkoxylatedbisphenols, such as but not limited to alkoxylated4,4′-isopropylidenediphenol which can have from 1 to 70 alkoxy groups,for example, ethoxy, propoxy, α-butoxy and β-butoxy groups; andbiscyclohexanols, which can be prepared by hydrogenating thecorresponding bisphenols, such as but not limited to4,4′-isopropylidene-biscyclohexanol, 4,4′-oxybiscyclohexanol,4,4′-thiobiscyclohexanol and bis(4-hydroxycyclohexanol)methane;polyurethane or polyurethane urea polyols, polyester polyols, polyetherpolyols, poly vinyl alcohols, polymers containing hydroxy functionalacrylates, polymers containing hydroxy functional methacrylates, andpolymers containing allyl alcohols.

In a non-limiting embodiment, the polyol can be chosen frommultifunctional polyols, including but not limited totrimethylolpropane, ethoxylated trimethylolpropane, pentaerythritol.

In alternate non-limiting embodiments, the polyurethane prepolymer canhave a number average molecular weight (Mn) of less than 50,000grams/mole, or less than 20,000 grams/mole, or less than 10,000grams/mole. The Mn can be determined using a variety of known methods.In a non-limiting embodiment, the Mn can be determined by gel permeationchromatography (GPC) using polystyrene standards.

In alternate non-limiting embodiments, the hydroxyl-containing materialfor use in the present invention can be chosen from polyether glycolsand polyester glycols having a number average molecular weight of atleast 200 grams/mole, or at least 300 grams/mole, or at least 750grams/mole; or no greater than 1,500 grams/mole, or no greater than2,500 grams/mole, or no greater than 4,000 grams/mole.

In a further non-limiting embodiment, polyether glycols for use in thepresent invention can include but are not limited to polytetramethyleneether glycol.

In a non-limiting embodiment, the hydroxyl-containing material caninclude both hydroxyl and thiol groups, such as but not limited to2-mercaptoethanol, 3-mercapto-1,2-propanediol, glycerinbis(2-mercaptoacetate) and 1-hydroxy-4-mercaptocyclohexane.

In general, polyurethanes and polyurethane prepolymers can bepolymerized using a variety of techniques known in the art. In anon-limiting embodiment of the present invention, the polymerizationprocess can include the use of an amine-containing material for curing.

Amine-containing curing agents for use in the present invention arenumerous and widely varied. Non-limiting examples of suitableamine-containing curing agents can include but are not limited toaliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines andmixtures thereof. In alternate non-limiting embodiments, theamine-containing curing agent can be a polyamine having at least twofunctional groups independently chosen from primary amine (—NH₂),secondary amine (—NH—) and combinations thereof. In a furthernon-limiting embodiment, the amine-containing curing agent can have atleast two primary amine groups. In another non-limiting embodiment, theamine-containing curing agent can comprise a mixture of a polyamine andat least one material selected from a polythiol and polyol. Non-limitingexamples of suitable polythiols and polyols include those previouslyrecited herein. In still another non-limiting embodiment, theamine-containing curing agent can be a sulfur-containingamine-containing curing agent. A non-limiting example of asulfur-containing amine-containing curing agent can include Ethacure 300which is commercially available from Albemarle Corporation.

Suitable amine-containing curing agents for use in the present inventioncan include but are not limited to materials having the followingchemical formula:

wherein R₁ and R₂ can each be independently chosen from methyl, ethyl,propyl, and isopropyl groups, and R₃ can be chosen from hydrogen andchlorine. Non-limiting examples of amine-containing curing agents foruse in the present invention include the following compounds,manufactured by Lonza Ltd. (Basel, Switzerland):

LONZACURE.RTM. M-DIPA: R₁═C₃H₇; R₂═C₃H₇; R₃═H

LONZACURE.RTM. M-DMA: R₁═CH₃; R₂═CH₃; R₃═H

LONZACURE.RTM. M-MEA: R₁═CH₃; R₂═C₂H₅; R₃═H

LONZACURE.RTM. M-DEA: R₁═C₂H₅; R₂═C₂HS; R₃═H

LONZACURE.RTM. M-MIPA: R₁═CH₃; R₂═C₃H₇; R₃═H

LONZACURE.RTM. M-CDEA: R₁═C₂H₅; R₂═C₂H₅; R₃═Cl

wherein R₁, R₂ and R₃ correspond to the aforementioned chemical formula.

In a non-limiting embodiment, the amine-containing curing agent caninclude but is not limited to a diamine curing agent such as4,4′-methylenebis(3-chloro-2,6-diethylaniline), (Lonzacure.RTM. M-CDEA),which is available in the United States from Air Products and Chemical,Inc. (Allentown, Pa.). In alternate non-limiting embodiments, theamine-containing curing agent for use in the present invention caninclude 2,4-diamino-3,5-diethyl-toluene, 2,6-diamino-3,5-diethyl-tolueneand mixtures thereof (collectively “diethyltoluenediamine” or “DETDA”),which is commercially available from Albemarle Corporation under thetrade name Ethacure 100; dimethylthiotoluenediamine (DMTDA), which iscommercially available from Albemarle Corporation under the trade nameEthacure 300; 4,4′-methylene-bis-(2-chloroaniline) which is commerciallyavailable from Kingyorker Chemicals under the trade name MOCA. DETDA canbe a liquid at room temperature with a viscosity of 156 cPs at 25° C.DETDA can be isomeric, with the 2,4-isomer range being from 75 to 81percent while the 2,6-isomer range can be from 18 to 24 percent.

Non-limiting examples of amine-containing curing agents can includeethyleneamines. Suitable ethyleneamines can include but are not limitedto ethylenediamine (EDA), diethylenetriamine (DETA),triethylenetetramine (TETA), tetraethylenepentamine (TEPA),pentaethylenehexamine (PEHA), piperazine, morpholine, substitutedmorpholine, piperidine, substituted piperidine, diethylenediamine(DEDA), and 2-amino-1-ethylpiperazine. In alternate non-limitingembodiments, the amine-containing curing agent can be chosen from one ormore isomers of C₁-C₃ dialkyl toluenediamine, such as but not limited to3,5-dimethyl-2,4-toluenediamine, 3,5-dimethyl-2,6-toluenediamine,3,5-diethyl-2,4-toluenediamine, 3,5-diethyl-2,6-toluenediamine,3,5-diisopropyl-2,4-toluenediamine, 3,5-diisopropyl-2,6-toluenediamine,and mixtures thereof. In alternate non-limiting embodiments, theamine-containing curing agent can be methylene dianiline ortrimethyleneglycol di(para-aminobenzoate).

In alternate non-limiting embodiments of the present invention, theamine-containing curing agent can include one of the following generalstructures:

In further alternate non-limiting embodiments, the amine-containingcuring agent can include one or more methylene bis anilines which can berepresented by the general formulas VII-XI, one or more aniline sulfideswhich can be represented by the general formulas XII-XVI, and/or one ormore bianilines which can be represented by the general formulasXVII-XX,

wherein R₃ and R₄ can each independently represent C₁ to C₃ alkyl, andR₅ can be chosen from hydrogen and halogen, such as but not limited tochlorine and bromine. The diamine represented by general formula VII canbe described generally as a 4,4′-methylene-bis(dialkylaniline). Suitablenon-limiting examples of diamines which can be represented by generalformula XII include but are not limited to4,4′-methylene-bis(2,6-dimethylaniline),4,4′-methylene-bis(2,6-diethylaniline),4,4′-methylene-bis(2-ethyl-6-methylaniline),4,4′-methylene-bis(2,6-diisopropylaniline),4,4′-methylene-bis(2-isopropyl-6-methylaniline) and4,4′-methylene-bis(2,6-diethyl-3-chloroaniline).

In a further non-limiting embodiment, the amine-containing curing agentcan include materials which can be represented by the following generalstructure (XXI):

where R₂₀, R₂₁, R₂₂, and R₂₃ can be independently chosen from H, C₁ toC₃ alkyl, CH₃—S— and halogen, such as but not limited to chlorine orbromine. In a non-limiting embodiment of the present invention, theamine-containing curing agent which can be represented by generalFormula XXI can include diethyl toluene diamine (DETDA) wherein R₂₃ ismethyl, R₂₀ and R₂₁ are each ethyl and R₂₂ is hydrogen. In a furthernon-limiting embodiment, the amine-containing curing agent can include4,4′-methylenedianiline.

In alternate non-limiting embodiments, the amine-containing material andblowing agent can be mixed with the polyisocyanate andhydroxyl-containing materials using a variety of methods and equipment,such as but not limited to an impeller or extruder. In a non-limitingembodiment, the mixing equipment can include a mechanical stirreroperating at low pressure such as less than 20 bar. In anothernon-limiting embodiment, the components can be mixed by impingementmixing wherein the components are injected at high velocity and pressureinto a mixing chamber, and the components are then mixed in the chamberby kinetic energy. In this embodiment, the components are typicallyinjected at a velocity of from 100 to 200 meters per second, and apressure of from 20 to 3000 bar.

In alternate non-limiting embodiments, polyurethane prepolymer andoptionally polyisocyanate can be contained in a first feed of a mixingunit, the amine-containing agent and optionally hydroxyl-containingmaterial in a second feed and the blowing agent in a third feed; or thesecond feed can include both the amine-containing material and theblowing agent, and optionally hydroxyl-containing material.

In another non-limiting embodiment, the polyurethane urea can beprepared by a one-pot process by combining polyisocyanate and/orpolyurethane prepolymer, hydroxyl-containing material, amine-containingmaterial and blowing agent.

In a non-limiting embodiment of the present invention, a mixing unithaving three feeds can be used in combining the polyisocyanate and/orpolyurethane prepolymer, hydroxyl-containing material, amine-containingmaterial and blowing agent. The ingredients can be added into the feedsusing a variety of configurations. In alternate non-limitingembodiments, the first feed of a mixing unit can contain polyisocyanateand/or polyurethane prepolymer and the second feed can containhydroxyl-containing material, amine-curing agent and blowing agent; orthe second feed can contain hydroxyl-containing material andamine-containing material, and a third feed can contain blowing agent;or the second feed can contain amine-containing material, and the thirdfeed can contain hydroxyl-containing material and blowing agent; or thesecond feed can contain hydroxyl-containing material, and the third feedcan contain amine-containing material and blowing agent. In furthernon-limiting embodiments, wherein polyurethane prepolymer is present ina first feed, the presence of hydroxyl-containing material in anotherfeed is optional.

A blowing agent can be used in the present invention to form cells atleast partially filled with gas within the polyurethane urea material.In a non-limiting embodiment, the cells are substantially uniformlydistributed throughout the polyurethane urea material. The size of thecells can vary widely. In alternate non-limiting embodiments, a cell canbe from at least 1 micron, or at least 20 microns, or at least 30microns, or at least 40 microns; to less than 1000 microns, or less than500 microns or less than 100 microns.

In a non-limiting embodiment, the blowing agent can be water. The watercan react in-situ with isocyanate (NCO) to produce carbon dioxide. In afurther non-limiting embodiment, one or more auxiliary blowing agentscan be used in combination with the blowing agent. Suitable auxiliaryblowing agents for use in the present invention can vary widely and caninclude substances which can be substantially volatile at the reactiontemperature. The auxiliary blowing agent can be selected from thoseknown in the art. Non-limiting examples can include but are not limitedto acetone, ethyl acetate, halogen substituted alkanes such as methylenechloride, chloroform, ethylidene chloride, vinylidene chloride,monofluorotrichloromethane, chlorodifluoromethane,dichlorodifluoromethane, dichloromonofluoromethane, butane, pentane,cyclopentane hexane, heptane, and diethylether.

The amount of blowing agent used in the present invention can vary. Inalternate non-limiting embodiments, the blowing agent can be present inan amount such that a selected or desired density and/or pore volume ofthe polishing pad can be achieved. In alternate non-limitingembodiments, the density can be from 0.50 to 1.10 g/cc; the pore volumecan be from 5% to 55% based on volume of polyurethane urea material.Density can be measured using a variety of methods known to one ofordinary skill in the art. The density values recited herein aredetermined in accordance with ASTM 1622-88. Pore volume can also bemeasured using a variety of methods known to a skilled artisan. The porevolume values recited herein are determined in accordance with ASTM D4284-88, using an Autopore III mercury porosimeter manufactured byMicromeritics. In a further non-limiting embodiment, the amount ofblowing agent can be from 0 to 5% by weight of the reaction mixture.

In a non-limiting embodiment, the amine-containing material can containat least a small concentration of residual moisture or water sufficientto act as the blowing agent.

In another non-limiting embodiment, a urethane-forming catalyst and/orblowing catalyst can be used in the present invention to enhance thereaction of the polyurethane urea-forming materials, and/or acceleratethe reaction with blowing agent. In a further non-limiting embodiment,one or more materials can be used wherein each material can exhibitcharacteristics of a urethane-forming and blowing catalyst.

Suitable urethane-forming catalysts can vary widely, for example,suitable urethane-forming catalysts can include those catalysts that areknown in the art to be useful for the formation of urethane by reactionof the NCO and OH-containing materials. Non-limiting examples ofsuitable catalysts can be chosen from the group of Lewis bases, Lewisacids and insertion catalysts as described in Ullmann's Encyclopedia ofIndustrial Chemistry, 5^(th) Edition, 1992, Volume A21, pp. 673 to 674.In a non-limiting embodiment, the catalyst can be a stannous salt of anorganic acid, such as but not limited to stannous octoate, dibutyl tindilaurate, dibutyl tin diacetate, dibutyl tin mercaptide, dibutyl tindimaleate, dimethyl tin diacetate, dimethyl tin dilaurate, and mixturesthereof. In alternate non-limiting embodiments, the catalyst can be zincoctoate, bismuth, or ferric acetylacetonate.

Non-limiting examples of suitable blowing catalysts can include tertiaryamines such as but not limited to 1,4-diazabicyclo[2.2.2]octane,bis-2-dimethyl aminoethyl ether, pentamethyldiethylene triamine,triethylamine, triisopropylamine, N-methylmorpholine andN,N-dimethylbenzylamine. Such suitable tertiary amines are disclosed inU.S. Pat. No. 5,693,738 at column 10, lines 6-38, the disclosure ofwhich is incorporated herein by reference. Tertiary amine catalysts mayalso include those containing hydroxyl functionality such asN,N-dimethylethanolamine, 2-(2-dimethylaminoethoxy-)ethanol,N,N,N′-trimethyl-N′-hydroxyethyl-bisaminoether,N,N-(dimethyl)-N,N′-diisopropanol-1,3-propanediamine, andN,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine.

In a non-limiting embodiment the catalyst can be chosen from phosphines,tertiary ammonium salts and tertiary amines, such as but not limited totributyl phosphine, triethylamine; triisopropylamine andN,N-dimethylbenzylamine. Additional non-limiting examples of suitabletertiary amines are disclosed in U.S. Pat. No. 5,693,738 at column 10lines 6 through 38, the disclosure of which is incorporated herein byreference.

In another non-limiting embodiment, a surfactant can be present duringpolymerization. Surfactants can influence the formation andstabilization of the at least partially gas-filled cells. In anon-limiting embodiment, the surfactant can be selected such that it hashigh surface activity for nucleation and stabilization of the cells. Inanother non-limiting embodiment, the surfactant can be selected suchthat it has good emulsifying abilities for a blowing agent. Suitablesurfactants for use in the present invention are wide and varied. In anon-limiting embodiment, a silicone surfactant can be used. The siliconesurfactant can be selected from siloxane-polyoxyalkylene copolymersurfactants. Non-limiting examples of such surfactants can include butare not limited to polydimethylsiloxane-polyoxyalkylene block copolymerswhich are available from GE Silicons Incorporated under the designationsNiax RTM. Silicone L-1800, L-5420 and L-5340; Dow Corning Corporationunder the designations DC-193, DC-5357 and DC-5315; and GoldschmidtChemical Corporation under the designations B-8404 and B-8407.

In a further non-limiting embodiment, the siloxane-polyoxyalkylenecopolymer surfactant can be represented by the following generalformula,

wherein x is a number from 1 to 150, y is a number of from 1 to 50, theratio of x:y is from 10:1 to 1:1 and R is an alkyl alkoxylate. Withreference to the general formula I, x can be from 10 to 50, or from 10to 42, or from 13 to 42; and y can be from 2 to 20, or from 5 to 20, orfrom 7 to 20, or from 7 to 10. The ratio of x:y can be between 2.4 and6.8.

R can be an alkyl alkoxylate which can be represented by the followinggeneral formula XXIII,R′O(C₂H₄O)_(m)(C₃H₆O)_(n)H  (XXIII)

wherein R′ is an alkylene group containing from 3 to 6 carbon atoms, mis a number of from 5 to 200, and n is a number of from 0 to 20, or from2 to 18. The molecular weight of R is in the range of from 400 to 4000,and the molecular weight of the surfactant represented by generalformula XXII can be from 6,000 to 50,000.

The siloxane-polyoxyalkylene copolymer surfactant can be prepared asdescribed in U.S. Pat. No. 5,691,392, column 3, line 25 through column4, line 18, which is incorporated herein by reference.

The amount of surfactant useful in the present invention can varywidely. In alternate non-limiting embodiments, the amount is such thatthe surfactant is from 0.001% to 10%, or 0.01% to 1%, or from 0.05% to0.5% by weight of the reaction mixture.

In another non-limiting embodiment, a nucleating agent can be usedduring polymerization in preparing the polyurethane urea of the presentinvention. Suitable nucleating agents for use in the present inventioncan include materials which enhance the generation of relatively smallsubstantially uniform cells. The nucleating agent can be selected fromthose known in the art. Non-limiting examples can include but are notlimited to relatively small size polymer particles such as but notlimited to polypropylene, polyethylene, polystyrene, polyurethane,polyester, and polyacrylates. The amount of nucleating agent used canvary widely. In general, the nucleating agent can be used in an amountwhich is effective to generate said cells. In alternate non-limitingembodiments, the nucleating agent can be present in an amount of from0.01% to 1.00%, or from 0.05% to 0.5%, by weight of the reactionmixture.

In a non-limiting embodiment, feeds containing polyisocyanate and/orpolyurethane prepolymer, hydroxyl-containing material, amine-containingmaterial, blowing agent and any optional additives can be directed intoa mixing unit. Optional additives can include a wide variety ofadditives known to one having ordinary skill in the art. Non-limitingexamples can include but are not limited to antioxidants, hindered amineUV stabilizers, UV absorbers, plasticizers, internal mold releaseagents, dyes and pigments. In further alternate non-limitingembodiments, any or all of the feeds can be heated to reduce theviscosity of the feeds and/or the resulting mixture. The reactionmixture exiting the mixing unit then can be poured into an open cavityto form a polishing pad. In a non-limiting embodiment, the cavity can becontrolled to a temperature of from 22° C. to 150° C., or from 60° C. to110° C.

The polishing pad of the present invention can have one or more worksurfaces, wherein “work surface” as used herein and the claims refers toa surface of the pad that can come into contact with the surface of thearticle that is to be polished and a polishing slurry. In a non-limitingembodiment, the article to be polished can be a silicon wafer. Infurther non-limiting embodiments, the work surface of the polishinglayer can have surface features such as but not limited to channels,grooves, perforations and combinations thereof.

Surface features can be incorporated into the work surface of thepolishing layer by means that are known to those of ordinary skill inthe art. In a non-limiting embodiment, the work surface can bemechanically modified, for example, by abrading or cutting. In anothernon-limiting embodiment, surface features can be incorporated into thework surface during the molding process, for example, by providing atleast one interior surface of the mold with raised features that can beimprinted into the work surface during its formation. Surface featurescan be distributed in the form of random or uniform patterns across thework surface. Non-limiting examples of surface feature patterns caninclude but are not limited to spirals, circles, squares, cross-hatchesand waffle-like patterns.

In a non-limiting embodiment, the polyurethane urea can comprise anabrasive particulate material. The abrasive particulate material can bedistributed substantially uniformly or non-uniformly throughout thepolyurethane urea. In alternate non-limiting embodiments, the abrasiveparticulate material can be present in an amount of less than 70 percentby weight, or at least 5 percent by weight, or from 5 percent to 65percent by weight, based on the total weight of the polishing pad.

In alternate non-limiting embodiments, the abrasive particulate materialcan be in the form of individual particles, aggregates of individualparticles, or a combination of individual particles and aggregates. Infurther alternate non-limiting embodiments, the shape of the abrasiveparticulate material can include but is not limited to spheres, rods,triangles, pyramids, cones, regular cubes, irregular cubes, and mixturesand/or combinations thereof.

In general, the average particle size of the Abrasive particulatematerial can vary widely. In alternate non-limiting embodiments, theaverage particle size can be at least 0.001 micron, or at least 0.01micron, or at least 0.1 micron. In further alternate non-limitingembodiments, the average particle size of the abrasive particulatematerial can be less than 50 microns, or less than 10 microns, or lessthan 1 micron. In a non-limiting embodiment, the average particle sizeof the abrasive particulate material can measured along the longestdimension of the particle.

Non-limiting examples of suitable abrasive particulate materials for usein the present invention can include aluminum oxide, such as but notlimited to gamma alumina, fused aluminum oxide, heat treated aluminumoxide, white fused aluminum oxide, and sol gel derived alumina; siliconcarbide, such as but not limited to green silicon carbide and blacksilicon carbide; titanium diboride; boron carbide; silicon nitride;tungsten carbide; titanium carbide; diamond; boron nitride, such as butnot limited to cubic boron nitride and hexagonal boron nitride; garnet;fused alumina zirconia; silica, such as but not limited to fumed silica;iron oxide; cromia; ceria; zirconia; titania; tin oxide; manganeseoxide; and mixtures thereof. In a further non-limiting embodiment, theabrasive particulate material can be chosen from aluminum oxide, silica,cerium oxide, zirconia and mixtures thereof.

In a non-limiting embodiment, the abrasive particulate material used inthe present invention can have a surface modifier thereon. Non-limitingexamples of suitable surface modifiers can include surfactants, couplingagents and mixtures thereof. In a non-limiting embodiment, surfactantscan be used to improve the dispersibility of the abrasive particles inthe polyurethane urea. In another non-limiting embodiment, couplingagents can be used to enhance binding of the abrasive particles to thematrix of the polyurethane urea. In further non-limiting embodiments,the surface modifier can be present in an amount of less than 25 percentby weight, or from 0.5 to 10 percent by weight, based on the totalweight of the abrasive particulate material and surface modifier.

Non-limiting examples of suitable surfactants for use as surfacemodifiers in the present invention can include anionic, cationic,amphoteric and nonionic surfactants, such as but not limited to metalalkoxides, polalkylene oxides, salts of long chain fatty carboxylicacids. Non-limiting examples of suitable coupling agents for use in thepresent invention can include silanes, such as but not limited toorganosilanes, titanates and zircoaluminates. In a non-limitingembodiment, the coupling agent can include SILQUEST Silanes A-174 andA-1230, which are commercially available from Witco Corporation.

In a further non-limiting embodiment, the thickness of the polishinglayer can vary from 0.5 mm to 5 mm.

In a non-limiting embodiment, the polishing layer can have a density offrom 0.5 grams per cubic centimeter (g/cc) to 1.1 g/cc as measured byASTM 1622-88. In another non-limiting embodiment, the polishing layercan have a Shore A Hardness value of at least 80, or from 85 to 98, andShore D Hardness value of at least 35, or 85 or less, or from 45 to 80,as determined in accordance with ASTM D 2240.

While not intending to be bound by any theory, it is believed that whenin use, while polishing or planarizing the surface of a silicon wafer,the porosity of the work surface of the polishing layer can remainsubstantially constant. As the work surface of the polishing pad is wornaway during, for example a polishing or pad conditioning process, newsurface pores are formed as those embedded pores residing proximatelybelow the work surface are exposed. Further, as the work surface of thepolishing pad is worn away during the polishing process, the gascontained within the at least partially gas-filled cells can be exposed.The gas can be released into the work environment and the remainingvoid(s) can be at least partially filled with polishing slurry.

The polishing pad of the present invention includes a second layer atleast partially connected to the polishing layer. The second layer caninclude a variety of materials known in the art. The second layer can beselected from substantially non-volume compressible polymers andmetallic films and foils. As used herein and the claims, “substantiallynon-volume compressible” means that the volume can be reduced by lessthan 1% when a load of 20 psi is applied.

Non-limiting examples of substantially non-volume compressible polymerscan include polyolefins, such as but not limited to low densitypolyethylene, high density polyethylene, ultra-high molecular weightpolyethylene and polypropylene; polyvinylchloride; cellulose-basedpolymers, such as but not limited to cellulose acetate and cellulosebutyrate; acrylics; polyesters and co-polyesters, such as but notlimited to PET and PETG; polycarbonate; polyamides, such as but notlimited to nylon 6/6 and nylon 6/12; and high performance plastics, suchas but not limited to polyetheretherketone, polyphenylene oxide,polysulfone, polyimide, and polyetherimide; and mixtures thereof.

Non-limiting examples of metallic films can include but are not limitedto aluminum, copper, brass, nickel, stainless steel, and combinationsthereof.

The thickness of the second layer can vary. In alternate non-limitingembodiments, the second layer can have a thickness of at least 0.0005,or at least 0.0010; or 0.0650 inches or less, or 0.0030 inches or less.

In a non-limiting embodiment, the second layer can be flexible toenhance or increase the uniformity of contact between the polishing padand the surface of the substrate being polished. A consideration inselecting the material for the second layer can be the capability of amaterial to provide compliant support to the work surface of thepolishing pad such that the polishing pad substantially conforms to themacroscopic contour or long-term surface of the device being polished. Amaterial having said capability can be desirable for use as the secondlayer in the present invention.

The flexibility of the second layer can vary. The flexibility can bedetermined using a variety of conventional techniques known in the art.As used herein and the claims the term “flexibility” (F) refers to theinverse relationship of the second layer thickness cubed (t³) and theflexural modulus of the second layer material (E), i.e. F=1/t³E. Inalternate non-limiting embodiments, the flexibility of the second layercan be at least 0.5 in⁻¹lb⁻¹; or at least 100 in⁻¹lb⁻¹; or from 1in⁻¹lb⁻¹ to 100 in⁻¹lb⁻¹.

In a non-limiting embodiment, the second layer can have acompressibility which allows the polishing pad to substantially conformto the surface of the article to be polished. The surface of amicroelectronic substrate, such as a semiconductor wafer, can have a“wave” contour as a result of the manufacturing process. It iscontemplated that if the polishing pad cannot adequately conform to the“wave” contour of the substrate surface, the uniformity of the polishingperformance can be degraded. For example, if the pad substantiallyconforms the ends of the “wave”, but cannot substantially conform andcontact the middle portion of the “wave”, only the ends of the “wave”can be polished or planarized and the middle portion can remainsubstantially unpolished or unplanarized.

The compressibility of the second layer can vary. The term“compressibility” refers to the percent volume compressibilitymeasurement when a load of 20 psi is applied. In alternate non-limitingembodiments, the percent volume compressibility of the second layer canbe at least one percent; or three percent or less; or from one to threepercent. The percent volume compressibility can be determined using avariety of conventional methods known in the art.

In a non-limiting embodiment, the second layer is substantiallynon-volume compressible.

In another non-limiting embodiment, the second layer can distribute thecompressive forces experienced by the polishing pad over a larger areaof a sub-pad layer.

In a non-limiting embodiment, the polishing pad of the present inventioncan be used without a sub-pad layer. The polishing pad without a sub-padlayer can be placed directly on the platen of a motorized polishingtool, machine, or apparatus. In a further non-limiting embodiment, thepolishing pad can be included in a polishing pad assembly, wherein abacking layer can be adhered to the back surface of the polishing pad.In a non-limiting embodiment, a polishing pad assembly can comprise:

(a) a polishing pad having a work surface and a back surface;

(b) a backing layer having an upper surface and a lower surface; and

(c) an adhesive means interposed between and in contact with at least aportion of the back surface of said polishing pad and at least a portionof the upper surface of said backing layer.

In a non-limiting embodiment, the backing sheet of the polishing padassembly can be rigid or flexible, and can support or stabilize orcushion the polishing pad during polishing operations. The backing sheetcan be fabricated from materials that are known to the skilled artisan.In alternate non-limiting embodiments, the backing sheet can befabricated from organic polymeric materials, such as but not limited topolyesters, such as polyethylene terephthalate sheet, and polyolefins,such as polyethylene sheet and polypropylene sheet.

In another non-limiting embodiment, the backing sheet of the polishingpad assembly of the present invention can be a release sheet, which canbe peeled away from the adhesive means, thereby allowing the pad to beadhered to another surface, for example, the platen of a polishingapparatus, by means of the exposed adhesive means. In general, releasesheets are known to those of ordinary skill in art. In a non-limitingembodiment, the release sheet can be fabricated from paper or organicpolymeric materials, such as but not limited to polyethyleneterephthalate sheet, polyolefins, for example, polyethylene sheet andpolypropylene sheet, and fluorinated polyolefins, for example,polytetrafluoroethylene. In a further non-limiting embodiment, the uppersurface of the release sheet can comprise a release coating thereon thatcan be in contact with the adhesive means. Release coatings are wellknown to the skilled artisan. Non-limiting examples of release coatingscan include fluorinated polymers and silicones.

The adhesive can be chosen from a wide variety of adhesive materialsknown in the art. A suitable adhesive for use in the present inventioncan provide sufficient peel resistance such that the pad layersessentially remain in place during use. Further, the adhesive can beselected to sufficiently withstand shear stresses which are presentduring the polishing or planarization process and moreover, cansufficiently resist chemical and moisture degradation during use. Theadhesive can be applied using conventional techniques known to theskilled artisan. In a non-limiting embodiment, the adhesive can beapplied to a lower surface of the polishing pad and/or an upper surfaceof the second layer which are parallel facing to one another.

Non-limiting examples of suitable adhesive means can include but notlimited to contact adhesives, pressure sensitive adhesives, structuraladhesives, hot melt adhesives, thermoplastic adhesives, and curableadhesives, such as thermosetting adhesives. Non-limiting examples ofstructural adhesives can be chosen from polyurethane adhesives, andepoxy resin adhesives; such as those based on the diglycidyl ether ofbisphenol A. Non-limiting examples of pressure sensitive adhesives caninclude an elastomeric polymer and a tackifying resin.

The elastomeric polymer can be chosen from natural rubber, butyl rubber,chlorinated rubber, polyisobutylene, poly(vinyl alkyl ethers), alkydadhesives, acrylics such as those based on copolymers of 2-ethylhexylacrylate and acrylic acid, block copolymers such asstyrene-butadiene-styrene, and mixtures thereof. In a non-limitingembodiment, a pressure sensitive adhesive can be applied to a substrateusing an organic solvent such as toluene or hexane, or from awater-based emulsion or from a melt. As used herein, “hot melt adhesive”refers to an adhesive comprised of a nonvolatile thermoplastic materialthat can be heated to a melt, then applied to a substrate as a liquid.Non-limiting examples of hot melt adhesives can be chosen fromethylene-vinyl acetate copolymers, styrene-butadiene copolymers,ethylene-ethyl acrylate copolymers, polyesters, polyamides such as thoseformed from the reaction of a diamine and a dimer acid, andpolyurethanes.

In a non-limiting embodiment, the adhesive layer can be applied to theback surface of the polishing pad and/or the upper surface of thebacking sheet, prior to pressing the polishing pad and backing sheettogether.

In alternate non-limiting embodiments, the adhesive means of thepolishing pad assembly can be selected from an adhesive assembly or anadhesive layer.

In further non-limiting embodiment, the adhesive assembly can comprisean adhesive support sheet interposed between an upper adhesive layer anda lower adhesive layer. The upper adhesive layer of the adhesiveassembly can be in contact with the back surface of the polishing pad,and the lower adhesive layer can be in contact with the upper surface ofthe backing sheet. Non-limiting examples of adhesive support sheets canbe fabricated from an organic polymeric material, such as but notlimited to polyesters, for example, polyethylene terephthalate sheet,and polyolefins, for example, polyethylene sheet and polypropylenesheet. In a further non-limiting embodiment, the upper and loweradhesive layers of the adhesive assembly can be chosen from thoseadhesives as recited previously herein with regard to the adhesivelayer. In a non-limiting embodiment, the upper and lower adhesive layerscan each be contact adhesives. In a further non-limiting embodiment, theadhesive assembly can be a two-sided or double-coated tape, such as butnot limited to double-coated film tapes, which can be commerciallyobtained from 3M, Industrial Tape and Specialties Division.

At least a portion of the polishing pad of the present inventionincludes an at least partially transparent window. In a non-limitingembodiment of the present invention, the polishing layer can comprise anopening. In a further non-limiting embodiment, at least a portion of thesecond layer can comprise a window which is at least partiallytransparent to wavelengths used by the metrology instrumentation of theplanarizing equipment. The opening in the polishing layer can at leastpartially align with the window in the second layer. The size, shape,and positioning of the opening in the polishing layer and/or the windowin the second layer can be dependent upon the metrology instrumentationand polishing apparatus being employed to polish and/or planarize thepad. The opening in the polishing layer can be produced by a variety ofconventional methods known in the art. In alternate non-limitingembodiments, the opening can be made by punching, die cutting, lasercutting or water jet cutting. In a further non-limiting embodiment, theopening can be formed when molding the polishing layer. In an alternatenon-limiting embodiment, the opening can be die cut into the polishinglayer using an NAEF Model B die press fitted with dies of suitable sizeand shape, which are commercially available from MS Instruments Company,Stony Brook, N.Y.

In a non-limiting embodiment, the opening in the polishing layer can beproduced prior to stacking together and/or at least partially connectingthe polishing layer with the second layer.

At least a portion of the second layer can comprise an at leastpartially transparent window. In a non-limiting embodiment, the secondlayer can comprise an at least partially transparent material. Inanother non-limiting embodiment, the second layer can comprise asubstantially non-transparent material; an opening can be cut into thesecond layer to remove a portion of the second layer; an at leastpartially transparent material can be inserted into the opening in thesecond layer. The opening can be made using a variety of methodspreviously described herein. In a non-limiting example, the second layercan include a metal foil; an opening can be cut into the metal foil toremove a portion of the metal foil; a piece of polyester can be cut intoa size and shape that substantially corresponds to the opening; thepolyester can be fitted into the opening in the metal foil to form an atleast partially transparent window.

In a non-limiting embodiment, the second layer can comprise an adhesiveassembly. The adhesive assembly can include interposing a middle layerbetween an upper adhesive layer and a lower adhesive layer. In anon-limiting embodiment, the upper adhesive layer of the adhesiveassembly can be at least partially connected to the lower surface of thepolishing layer. In a non-limiting embodiment, the lower adhesive layerof the adhesive assembly can be at least partially connected to theplaten of the polishing tool. In another non-limiting embodiment, thelower adhesive layer of the adhesive assembly can be at least partiallyconnected to the upper surface of a sub-pad layer. The middle layer ofthe adhesive assembly can be selected from the aforementioned suitablematerials for the second layer of the polishing pad. The upper and loweradhesive layers of the adhesive assembly can be selected from thenon-limiting examples of adhesives previously mentioned herein. In anon-limiting embodiment, the upper and lower adhesive layers each can becontact adhesives. The adhesive assembly can be referred to in the artas two-sided or double-coated tape. Non-limiting examples ofcommercially available adhesive assemblies include those from 3M,Industrial Tape and Specialties Division.

In a further non-limiting embodiment, at least a portion of the adhesivelayer can be removed from the second layer of the adhesive assemblyexposing at least a portion of the at least partially transparent middlelayer of the adhesive assembly, thereby forming an at least partiallytransparent window in the second layer. In alternate non-limitingembodiments, the removal of the adhesive can be performed prior tostacking the layers or after the layers are stacked. The removal processcan include a variety of methods known to the skilled artisan, includingbut not limited to dissolution of the adhesive in solvent or aqueousdetergent solution, or physically stripping the adhesive from the secondlayer. In a non-limiting embodiment, physically stripping the adhesivecan be include contacting the adhesive with a material to which theadhesive substantially adheres, and then pulling the material from thesecond layer, whereby the adhesive is removed with the material.

In a further non-limiting embodiment, the window of the second layer canbe recessed below the surface of the pad by a distance equal to thethickness of the polishing layer of the pad. In another non-limitingembodiment, the pad can include a coating on at least a portion of aside of the window of the second layer. The coating can be at leastpartially applied with an adhesive in place or following removal of theadhesive. The coating can be at least partially applied prior tostacking the layers or after the layers have been stacked. The coatingcan provide any one of the following properties, for example: improvedtransparency of the window area, improved abrasion resistance, improvedpuncture resistance.

In a non-limiting embodiment, the coating can include a resin film, or acast-in-place resin coating. Non-limiting examples of suitable resinfilms for use in the present invention can include the materialsdescribed above for the second layer. In alternative non-limitingembodiments, the resin film chosen for the coating can be the samematerial or different material as that comprising the second pad layer.The resin film can be at least partially adhered to the window area ofthe second layer by any means known to the skilled artisan, such as theadhesive methods and materials listed above for pad stack adhesives. Ina non-limiting embodiment, the coating can be a layer of resin film thatcan be the same as the material used for the second layer. The coatingcan be at least partially applied after assembly of the pad stack. Thecoating can be at least partially applied to both the top and bottomsurfaces of the window area of the second layer, and the adhesive can beat least partially adhered using a contact adhesive used as the stackadhesive.

In a non-limiting embodiment, the coating can be a cast-in-place resincoating, which can be applied as a liquid, as a solvent solution,dispersion, or aqueous latex, as a melt, or as a blend of resinprecursors that can react to form the coating. The application of theliquid can be accomplished by a variety of known methods, includingspraying, padding, and pouring. Non-limiting examples of suitablematerials for the coating include thermoplastic acrylic resins,thermoset acrylic resins, such as hydroxyl-functional acrylic latexescrosslinked with urea-formaldehyde or melamine-formaldehyde resins,hydroxyl-functional acrylic resins crosslinked with epoxy resins, orcarboxyfunctional acrylic latexes crosslinked with carbodiimides orpolyimines or epoxy resins; urethane systems, such as hydroxyfunctionalacrylic resin crosslinked with polyisocyanate, moisture-curedisocyanate-terminated resins; carbamate-funtional acrylic resinscrosslinked with melamine-formaldehyde resins; epoxy resins, such aspolyamide resin crosslinked with bisphenol A epoxy resins, phenolicresins crosslinked with bisphenol A epoxy resins; polyester resins, suchas hydroxyl-terminated polyesters crosslinked with melamine-formaldehyderesins or with polyisocyanates or with epoxy crosslinkers.

In a non-limiting embodiment, the coating can be an aqueous acryliclatex, which can be applied following stacking of the pad assembly. Thecoating can be at least partially applied to the top and bottom surfacesof the window area of the second layer. Application of the coating canbe performed following removal of an adhesive from the window area.

In another non-limiting embodiment, the polishing pad of the presentinvention can include a sub-pad layer. The sub-pad layer can be at leastpartially connected to the second layer, and the second layer can be atleast partially connected to the polishing layer. In a non-limitingembodiment, the second and/or sub-pad layers can be at least partiallyconnected by an adhesive means. Suitable adhesive means can includethose previously described herein. In a further non-limiting embodiment,a sub-pad layer can be used to increase the uniformity of contactbetween the polishing pad and the surface of the substrate which isbeing polished. The sub-pad layer can be made of a compressible materialcapable of imparting substantially even pressure to the work surface ofthe polishing pad. Non-limiting examples of sub-pad layers can includebut are not limited to polyurethane or polyurethane urea impregnatedfelt, and foam sheet made of natural rubber, synthetic rubber,thermoplastic elastomer; or combinations thereof.

In alternate non-limiting embodiments, the material of the sub-pad layercan be foamed or blown to produce a porous structure. The porousstructure can be open cell, closed cell, or combinations thereof.

Non-limiting examples of synthetic rubbers can include neoprene rubber,silicone rubber, chloroprene rubber, ethylene-propylene rubber, butylrubber, polybutadiene rubber, polyisoprene rubber, EPDM polymers,styrene-butadiene copolymers, copolymers of ethylene and ethyl vinylacetate, neoprene/vinyl nitrile rubber, neoprene/EPDM/SBR rubber, andcombinations thereof. Non-limiting examples of thermoplastic elastomerscan include polyurethanes such as those based on polyethers andpolyesters, and copolymers thereof. Non-limiting examples of foam sheetcan include polyurethane foam sheet and polyolefin foam sheets, such asbut not limited to those which are commercially available from RogersCorporation, Woodstock, Conn.

In a further non-limiting embodiment, the sub-pad layer can includenon-woven or woven fiber mat, and combinations thereof; such as but notlimited to polyolefin, polyester, polyamide, or acrylic fibers, whichhave been impregnated with a resin. The fibers can be staple orsubstantially continuous in the fiber mat. Non-limiting examples caninclude but are not limited to non-woven fabric impregnated withpolyurethane, such as polyurethane impregnated felt. A non-limitingexample of a commercially available non-woven sub-pad layer can be Suba™IV, from Rodel, Inc. Newark, Del.

The thickness of the sub-pad layer can vary widely. In general, thesub-pad layer thickness should be such that the stacked pad is not toothick. A stacked pad which is too thick can be difficult to place on andtake off of the planarization equipment. Thus, in a non-limitingembodiment, the thickness of the sub-pad layer can be from 0.2 to 2 mm.

In a non-limiting embodiment, the polishing pad of the present inventioncan comprise a sub-pad layer, and the sub-pad layer can function as thebottom layer of the pad which can be attached to the platen of thepolishing tool.

In a non-limiting embodiment, the sub-pad layer can be substantiallynonporous and substantially impermeable to polishing slurry. As usedherein and the claims, the term “substantially nonporous” meansgenerally impervious to the passage of liquid, gas, and bacteria. On amacroscopic scale, a substantially nonporous material exhibits few ifany pores. As used herein and the claims, the term “porous” means havingpore(s) and the term “pore(s)” refers to minute opening(s) through whichmatter passes.

In another non-limiting embodiment, a three-layer stacked pad can beconstructed by at least partially connecting the polishing layer to thesecond layer and at least partially connecting the second layer to asub-pad layer. In a further non-limiting embodiment, a 22.0″ diameterSUBA IV subpad commercially available from Rodel, Incorporated cancomprise the sub-pad layer. An opening can be cut into the polishinglayer, second layer and sub-pad layer as described previously herein. Ina further non-limiting embodiment, the opening can be rectangular inshape, having dimensions of 0.5″×2.0″, being positioned with the longaxis radially oriented and centered 4″ from the center of the pad. Awindow can be formed in the second layer as previously described herein.In alternate non-limiting embodiments, the opening can be cut into theSUBA IV pad prior to at least partially connecting it to the secondlayer, or the opening can be cut following at least partially connectingthe polishing layer, second layer and sub-pad layer.

In another non-limiting embodiment, the window can be formed in thepolishing layer and second layer assembly as previously describedherein, and the sub-pad layer containing an opening then can be at leastpartially connected to the second layer such that the opening in thesub-pad layer is at least partially aligned with the opening in thepolishing pad and window in the second layer. An opening can be cut intothe sub-pad prior to or after at least partially connecting the sub-padto the polishing pad and second layer assembly. In alternatenon-limiting embodiments, the opening can be produced by any suitablemeans known in the art, such as those previously identified relative tothe opening in the polishing layer. Further, as previously identified,the size, shape and position of the opening can be dependent upon themetrology instrumentation and polishing apparatus employed.

In another non-limiting embodiment, the polishing pad of the presentinvention can comprise a polishing layer, a second layer, and a sub-padlayer. The polishing and sub-pad layers can each comprise an opening.The openings in these two layers can be at least partially aligned withone another. At least a portion of the second layer can include an atleast partially transparent window. The window can be at least partiallycoated on both sides with contact adhesive, and the layers can bepressed together to form a stacked pad assembly. The adhesive can thenbe physically stripped from the top and bottom surface of the windowarea of the second layer using a material to which the adhesivesubstantially adheres. A non-limiting example of a material to which theadhesive substantially adheres is Teslin® SP-1000, a synthetic sheetmaterial which is commercially available from PPG Industries, Inc,Pittsburgh, Pa.

In a non-limiting embodiment, the polishing pad of the present inventioncan be used in combination with polishing slurries which are known inthe art. Non-limiting examples of suitable slurries for use with the padof the present invention, include but are not limited to the slurriesdisclosed in U.S. patent application having Ser. Nos. 09/882,548 and09/882, 549, which were both filed on Jun. 14, 2001 and are pending. Ina non-limiting embodiment, the polishing slurry can be interposedbetween the polishing pad and the substrate to be polished. Thepolishing or planarizing process can include moving the polishing padrelative to the substrate being polished. A variety of polishingslurries are known in the art. Non-limiting examples of suitableslurries for use in the present invention include slurries comprisingabrasive particles. Abrasives that can be used in the slurries includeparticulate cerium oxide, particulate alumina, particulate silica andthe like. Examples of commercial slurries for use in the polishing ofsemiconductor substrates include but are not limited to ILD1200 andILD1300 available from Rodel, Inc. Newark, Del. and Semi-Sperse AM100and Semi-Sperse 12 available from Cabot Microelectronics MaterialsDivision.

The window pad of the present invention can be used with a variety ofpolishing equipment known in the art. In a non-limiting embodiment, aMirra polisher, produced by Applied Materials Inc, Santa Clara, Calif.,can be used wherein the shape of the opening is a rectangle, having asize 0.5″×2″, being positioned with the long axis radially oriented andcentered 4″ from the center of the pad. The platen for the Mirrapolisher is 20″ in diameter. A pad for use with this polisher cancomprise a circle of a 20-inch diameter having a window located in thearea as described.

In a further non-limiting embodiment, a Teres polisher commerciallyavailable from Lam Research Corporation, Fremont, Calif., can beemployed. This polisher uses a continuous belt instead of a circularplaten. The pad for this polisher can be a continuous belt of 12″ widthand 93.25″ circumference, which has a window area suitably sized andpositioned to align with the metrology window of the Teres polisher canbe such that it can be at least partially aligned with the at leastpartially transparent window in the second layer.

The polishing pad of the present invention can have shapes chosen frombut not limited to circles, ellipses, squares, rectangles and triangles.In a non-limiting embodiment, the polishing pad can be in the form of acontinuous belt. The polishing pad according to the present inventioncan have a wide range of sizes and thicknesses. In a non-limitingembodiment, a circular polishing pad can have a diameter ranging from3.8 cm to 137 cm.

The present invention is more particularly described in the followingexamples, which are intended to be illustrative only, since numerousmodifications and variations therein will be apparent to those skilledin the art. Unless otherwise specified, all parts and all percentagesare by weight.

EXAMPLE Example 1

36.00 kilograms of Airthane PHP-75D polyurethane prepolymer, 1.26kilograms of Desmodur N 3300A and 0.19 kilograms of Niax L-1800surfactant were charged into the first tank of a Baule' three-componentlow pressure dispensing machine and held at 140° F. with 15 PSI ofnitrogen pressure. This tank was mixed with low agitation. A curativemixture was prepared by melting 35.5 kilograms of Lonzacure MCDEA at atemperature of 210° F. then 5.5 kilograms of Versalink P-250 were addedwith stirring. Next, 0.21 kilograms of Niax L1800 added and stirreduntil uniformly mixed. This curative mixture was then charged into thesecond tank and held at 210° F. with 40 psi of nitrogen pressure andmixed with low agitation. Then a mixture of 219 grams Versalink P-650,60 grams of DABCO BL-19 catalyst and 21 grams of deionized water werecharged into the third tank at ambient temperature and pressure. Thefluids of the first, second and third tanks were fed into a mixer, byconstant delivery pumps, at a weight ratio of 242 grams from the firsttank: 100 grams from the second tank: 1.80 grams from the third tank.The fluids were mixed under high agitation and dispensed into an opencircular mold having a diameter of 31 inches and a thickness of 0.090inches which had been preheated to 160° F. The open mold was placed inan oven at 160° F. for 15 minutes. After this time, the product wasremoved from the mold. Curing was continued for 18 hours at 230° F. Theproduct was then allowed to cool to ambient temperature. A circular padhaving a 20″ diameter was cut from the molded part. The pad was then cutto a thickness of 0.090 inches and the upper and lower surfaces of thepad were made parallel using a milling machine. Concentric circulargrooves 0.020″ wide×0.030″ deep with a pitch of 0.060″ were machinedinto the work surface. A window opening was then cut in the pad. Theshape of the opening was rectangular, having dimensions of 0.5″×2.0″,being positioned with the long axis radially oriented and centered 4″from the center of the pad. A layer of double-coated film tape withrelease liner was then applied to the surface of the disk which was notgrooved such that the rectangular opening in the first layer wassubstantially spanned by the tape. The film tape was commerciallyobtained from 3M as High Performance Double Coated Tape type 9500PC.

A stacked pad was constructed by mounting the polishing pad assembly ona third layer of subpad with opening. The subpad consisted of apolyurethane foam disk having a diameter of 20″ which was die cut from asheet of PORON FH 48 available from Rogers Corporation, Woodstock,Conn., having a thickness of 1.5 millimeters and a density of 0.48g/cm³. Another double-coated film tape with release liner wascommercially obtained from Adhesives Research, Inc. under the trade nameARclad 90334 was applied to one surface of the polyurethane foam. Awindow opening was then cut into the 20″ diameter foam pad and ARclad90334 tape with release liner. The shape of the opening was rectangular,having dimensions of 0.5″×2.0″, being positioned with the long axisradially oriented and centered 4″ from the center of the pad. Next, therelease liner of 3M 9500PC on the polishing pad assembly was removed,exposing the adhesive. The polishing pad assembly was then firmlybonded, with this adhesive, to the polyurethane foam side of the subpad.Care was taken during mounting so that the window opening in the subpadwas aligned with the pad window. The three-layer stack assembly was thenpassed through a calendar roll set. The adhesive on the upper and lowersides of the second layer in the window area was removed by contactingit with a ½×2″ rectangular piece of Teslin SP-1000, commerciallyavailable from PPG Industries, Incorporated. This was accomplished bypressing the piece by hand to ensure good contact between the adhesiveand the Teslin SP-1000, then peeling away the Teslin SP-1000. Theadhesive selectively adhered to the Teslin SP-1000, leaving thesubstantially clear film of the window free of adhesive. The resultingpad stack had a transparent rectangular window having a size of ½×2″.The remaining release liner on the subpad can be removed to permitattachment to a commercial planarizing apparatus.

1. A pad adapted to polish a microelectronic substrate, said padcomprising: a. a polyurethane urea-containing polishing layer, saidpolishing layer comprising at least partially gas-filled cells, at leasta portion of said at least partially gas-filled cells formed by anin-situ reaction, wherein an opening is formed in said polishing layer;and b. a second layer wherein at least a portion of said second layercomprises an at least partially transparent window, wherein saidpolishing layer is at least partially connected to said second layer,and said opening in said polishing layer is at least partially alignedwith said window of said second layer.
 2. A pad adapted to polish amicroelectronic substrate, said pad comprising: a. a polyurethaneurea-containing polishing layer, said polishing layer comprising atleast partially gas-filled cells, said polishing layer formed byreaction of polyurethane prepolymer with amine-containing material andblowing agent, wherein an opening is formed in said polishing layer; andb. a second layer wherein at least a portion of said second layercomprises an at least partially transparent window, wherein saidpolishing layer is at least partially connected to said second layer,and said opening in said polishing layer at least partially aligns withsaid window of said second layer.
 3. A pad adapted to polish amicroelectronic substrate, said pad comprising: a. a polyurethaneurea-containing polishing layer, said polishing layer comprising atleast partially gas-filled cells, said polishing layer formed byreaction of polyisocyanate with hydroxyl-containing material,amine-containing material and blowing agent, wherein an opening isformed in said polishing layer; and b. a second layer wherein at least aportion of said second layer comprises an at least partially transparentwindow, wherein said polishing layer is at least partially connected tosaid second layer, and said opening in said polishing layer at leastpartially aligns with said window of said second layer.
 4. A pad adaptedto polish a microelectronic substrate, said pad comprising: a. apolyurethane urea-containing polishing layer, said polishing layercomprising at least partially gas-filled cells, said polishing layerformed by reaction of polyisocyanate and polyurethane prepolymer,amine-containing material, blowing agent, and optionallyhydroxyl-containing material, wherein an opening is formed in saidpolishing layer; and b. a second layer wherein at least a portion ofsaid second layer comprises an at least partially transparent window,wherein said polishing layer is at least partially connected to saidsecond layer, and said opening in said polishing layer at leastpartially aligns with said window of said second layer.
 5. The pad ofclaim 1, wherein said polishing layer is formed by reaction ofhydroxyl-containing material, amine-containing material, blowing agentand at least one material selected from the group consisting ofpolyisocyanate, polyurethane prepolymer and mixtures thereof.
 6. The padof claim 1, wherein gas in at least a portion of said at least partiallygas-filled cells is exposed when at least a portion of a work surface ofsaid pad is at least partially worn away when said work surface is incontact with a substrate to be polished.
 7. The pad of claim 3 whereinsaid polyisocyanate has at least two isocyanate functional groups. 8.The pad of claim 3 wherein said polyisocyanate is selected from thegroup consisting of polymeric and C₂-C₂₀ linear, branched, cyclic andaromatic polyisocyanates.
 9. The pad of claim 2 wherein saidhydroxyl-containing material is selected from the group consisting ofpolyether polyols, polyester polyols, polycaprolactone polyols,polycarbonate polyols, and mixtures thereof.
 10. The pad of claim 2,wherein said amine-containing material is selected from the groupconsisting of aliphatic polyamines, cycloaliphatic polyamines, aromaticpolyamines and mixtures thereof.
 11. The pad of claim 2, wherein saidamine-containing material comprises a polyamine and at least onematerial selected from the group consisting of polythiol and polyol. 12.The pad of claim 2, wherein said amine-containing material furthercomprises sulfur.
 13. The pad of claim 2, further comprising at leastone material selected from urethane catalyst, blowing catalyst,surfactant, and nucleating agent.
 14. The pad of claim 1 wherein saidpad has a work surface and said surface comprises at least one featureselected from the group consisting of channels, grooves andperforations.
 15. The pad of claim 1 wherein said polyurethane ureacomprises abrasive particulate material.
 16. The pad of claim 15 whereinsaid abrasive particulate material is distributed substantiallyuniformly throughout said polyurethane urea.
 17. The pad of claim 15wherein said abrasive particulate material is present in an amount offrom 5% by weight to less than 70% by weight based on the total weightof the pad.
 18. The pad of claim 15 wherein said abrasive particulatematerial has an average particle size of from 0.001 micron to less than50 microns.
 19. The pad of claim 15 wherein said abrasive particulatematerial is silica.
 20. The pad of claim 1 wherein said second layer isselected from polyolefins, cellulose-based polymers, acrylics,polyesters and co-polyesters, polycarbonates, polyamides, plastics, andcombinations thereof.
 21. The pad of claim 1 wherein said second layeris selected from substantially non-compressible polymers, metallic filmsand foils, and combinations thereof.
 22. The pad of claim 1 furthercomprising a sub-pad layer having an opening formed therein, saidsub-pad layer at least partially connected to said second layer, andwherein said opening in said sub-pad layer at least partially alignswith said window of said second layer and said opening in said polishinglayer.
 23. The pad of claim 22 wherein said sub-pad layer is chosen fromnon-woven fiber mat, woven fiber mat, or combinations thereof.
 24. Thepad of claim 22 wherein said sub-pad layer is chosen from polyurethaneimpregnated felt, polyurethane urea impregnated felt, or combinationsthereof.
 25. The pad of claim 22 wherein said sub-pad layer is selectedfrom foam sheet containing natural rubbers, synthetic rubbers,thermoplastic elastomers or combinations thereof.
 26. A method ofpreparing a pad adapted to polish microelectronic substrates,comprising: a. forming a polyurethane urea-containing polishing layerwherein said polyurethane urea comprises at least partially gas-filledcells, and wherein at least a portion of said at least partiallygas-filled cells is formed by an in-situ reaction; b. forming an openingin said polishing layer; c. forming a second layer which comprises an atleast partially transparent window; d. at least partially aligning saidopening in said polishing layer and said window of said second layer;and e. at least partially connecting said polishing layer and saidsecond layer.
 27. The method of claim 26 wherein said polishing layer isformed by combining polyisocyanate with hydroxyl-containing material,amine-containing material and blowing agent to produce polyurethane ureawherein at least a portion of said urea contains at least partiallygas-filled cells.
 28. The method of claim 26 wherein said polishinglayer is formed by combining polyisocyanate with hydroxyl-containingmaterial to form polyurethane prepolymer; and combining saidpolyurethane prepolymer with amine-containing material and blowing agentto form polyurethane urea wherein at least a portion of said ureacontains at least partially gas-filled cells.
 29. The method of claim 27wherein said polishing layer is formed by combining polyisocyanate andpolyurethane prepolymer with hydroxyl-containing, amine-containingmaterial and blowing agent to form polyurethane urea wherein at least aportion of said urea contains at least partially gas-filled cells. 30.The method of claim 27 wherein ingredients are combined at a pressure ofless than 20 bar.
 31. The method of claim 28 wherein ingredients arecombined at a pressure of at least 20 bar.
 32. The method of claim 26wherein said at least partially gas-filled cells comprise carbondioxide.
 33. The method of claim 26 wherein said at least partiallygas-filled cells have an average size of from at least 1 micron to lessthan 100 microns.
 34. The method of claim 26 wherein said substantiallygas-filled cells are substantially uniformly distributed throughout saidpolyurethane urea.
 35. The method of claim 27 wherein said blowing agentcomprises water.
 36. The method of claim 28 wherein said blowing agentis water.
 37. The method of claim 27 further comprising adding anauxiliary blowing agent.
 38. The method of claim 28 further comprisingcombining said polyurethane prepolymer with an auxiliary blowing agent.39. The method of claim 37 wherein said auxiliary blowing agent isselected from the group consisting of acetone, ethyl acetate, andhalogen-substituted alkanes.
 40. The method of claim 38 wherein saidauxiliary blowing agent is selected from the group consisting ofacetone, ethyl acetate, and halogen-substituted alkanes.
 41. The methodof claim 26 further comprising: a. forming a sub-pad layer wherein anopening is formed therein; b. at least partially aligning said openingin said sub-pad layer with said window of said second layer and saidopening in said polishing layer; and c. at least partially connectingsaid sub-pad layer and said second layer.
 42. A pad assembly comprising:a. a polishing layer comprising polyurethane urea wherein at least aportion of said polyurethane urea comprises at least partiallygas-filled cells wherein at least a portion of said cells are formed byan in-situ reaction, said polishing layer having a work surface and aback surface; b. a backing sheet having an upper surface and a lowersurface; and c. an adhesive means interposed between and at leastpartially connecting said back surface of said polishing layer and anupper surface of said backing sheet, at least a portion of said adhesivemeans being at least partially transparent, wherein an opening is formedin each of said polishing layer and said backing sheet, and wherein saidopenings in each polishing layer and backing sheet are at leastpartially aligned with said transparent portion of said adhesive means,and wherein said polishing layer is at least partially connected to saidadhesive means and said adhesive means is at least partially connectedto said backing sheet.
 43. The pad assembly of claim 42 wherein saidpolyurethane urea is formed by combining hydroxyl-containing material,amine-containing material, blowing agent and at least one materialselected from the group consisting of polyisocyanate, polyurethaneprepolymer and mixtures thereof.